Telephoto lens for astrophotography.

[AstronomyUkraine]

After reading a few articles by members on here regarding widefield imaging, a germ of an idea popped into my head. I have at my disposal several Canon EOS L series lenses that I use for wildlife imaging. As anyone who has been into photography for any length of time knows, the L series lenses are high quality. The one I want to use is my 100 - 400 L IS USM. It is not extremely fast like the Samyang lens other members are using, but it is still a respectable f4.5, with a 77mm filter size.

 

My plan is to buy a ZWO-EFW-EOS-II adapter which will allow me to connect my EFW to the Canon lens, autofocus won't be an option, but I can use a Bahtinov mask, and the focusing mechanism on the lens is very good, allowing fine adjustments.

 

 

The only problem I can see is platesolving and finding the focus point, but this adapter is specially made for Canon cameras to operate with the EFW and the 1600 which I use. So hopefully the focusing shouldn't be a problem. The 100 - 400 lens also has a built in tripod mount, so bolting it down to a dovetail won't be a problem.

 

If I have overlooked anything, or anyone has any experience using this type of lens for astro imaging, let me know your thoughts.

 

Brian

[MarkAR]

I have the same lens, finding focus isn't too bad. Last time I messed around at night with it I forgot to take off the UV protective filter. I think this might have caused astigmatic looking stars.

[AstronomyUkraine]

10 hours ago, MarkAR said:

I have the same lens, finding focus isn't too bad. Last time I messed around at night with it I forgot to take off the UV protective filter. I think this might have caused astigmatic looking stars.

I have done that myself taking images of the moon. 😀

[Galileo]

I always used Canon lenses for some of my astrophotography and was happy with my results until I got an ASKAR ACL200 apo lens and realized that although Canon lenses are really good there are plentiful aberations that don't show up in normal photography. 

[paul]

On 6/12/2021 at 8:10 PM, AstronomyUkraine said:

After reading a few articles by members on here regarding widefield imaging, a germ of an idea popped into my head. I have at my disposal several Canon EOS L series lenses that I use for wildlife imaging. As anyone who has been into photography for any length of time knows, the L series lenses are high quality. The one I want to use is my 100 - 400 L IS USM. It is not extremely fast like the Samyang lens other members are using, but it is still a respectable f4.5, with a 77mm filter size.

 

My plan is to buy a ZWO-EFW-EOS-II adapter which will allow me to connect my EFW to the Canon lens, autofocus won't be an option, but I can use a Bahtinov mask, and the focusing mechanism on the lens is very good, allowing fine adjustments.

 

 

The only problem I can see is platesolving and finding the focus point, but this adapter is specially made for Canon cameras to operate with the EFW and the 1600 which I use. So hopefully the focusing shouldn't be a problem. The 100 - 400 lens also has a built in tripod mount, so bolting it down to a dovetail won't be a problem.

 

If I have overlooked anything, or anyone has any experience using this type of lens for astro imaging, let me know your thoughts.

 

Brian

 

[paul]

I have the same adapter but hooked up to the Samyang. I only got around to testing it in the last couple of weeks. First light was stupid because I left fitted the 10mm extension it comes with. Removing it at least allowed me to see trees in the distance, I had to add back a 0.5 mm spacer for it to focus on infinity. I haven't managed to take any images to check quality yet. (I have the stick-on dew-heater so I guess the total additional spacing is currently around 0.6mm).

 

Edited June 1, 2022 by paul

[paul]